Why does my SNMP device not return all data?
This may be caused by the inability of the device to return all the requested SNMP data.
The most common "fix" for this issue is to reduce the amount of data requested in each request by lowering the 'Max Repetitions' to 10.
Max Repetitions is a SNMPv2 GETBULK request tunable. It informs the remote device the maximum number of objects the servers SNMP engine can handle within a response. The SNMP engine can process full 16kbyte datagrams (ie. fragmented IP packets) and therefore very large max repetition values. A large max repetitions value results in a significantly faster and more efficient walk using GETBULK requests.
Unfortunately, due to the large number of vendor device bugs, the default max_repetitions value has been set to an arbitrary low value of 50.
Most other vendors or open source software use a tiny value of 10.
Known issues:
Devices incorrectly interpret max_repetitions as the number of objects it should respond with instead of applying its own response limits. This typically results in the device either not responding or crashing due to buffer overruns. This is a defect in the device and it should be reported to the vendor.
Large max_repetition values cause extremely high CPU load on some vendors devices when walking various MIB tables.
NOTE: This is a global SNMP engine tunable which is configurable in the SNMP Config area of the Administration page.
The SNMP engine contains per IP address tunables for:
Max Repetitions (default 50)
Inflight request/response window size (default 1) - this is not normally modified.
Format:
'{ipaddress}' '{max repetitions 1 to 100}' '{window size 1 to 10}'
Example:
'10.55.6.2' '10' '1'
Contact Technical Support for more details if required.